Arrangement and interface for RF ablation system with acoustic feedback

ABSTRACT

A system for ablation with acoustic feedback comprises: a catheter which includes an elongated catheter body; at least one ablation element to ablate a targeted tissue region; and a pulse-echo ultrasonic transducer arranged to emit and receive an acoustic beam along a centroid in a beam direction, at a transducer beam angle of between about 30 degrees and about 60 degrees relative to a distal direction of the longitudinal axis at a location of intersection between the longitudinal axis and the beam direction of the centroid of the acoustic beam of the ultrasonic transducer, wherein the transducer transmits and receives acoustic pulses to provide lesion information in the targeted tissue region; an ablation power subsystem; an ultrasonic transmit and receive subsystem to operate the ultrasonic transducer; a control subsystem to control operation of the ablation power subsystem and the ultrasonic transmit and receive subsystem; and a display.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 13/086,605, filed Apr. 14, 2011. This application is also acontinuation-in-part of U.S. patent application Ser. No. 13/113,170,filed May 23, 2011. The entire disclosures of these applications areincorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates generally to ablation devices and, morespecifically, to a combination catheter for forward and side lesioningwith acoustic or ultrasonic lesion feedback capability.

Current industry R&D in ultrasonic lesion feedback focuses ontransducers that look out from the ablation electrode tip both forwardlyand sideways. This requires the use of dual transducers in an ablationinstrument such as a catheter, resulting in a considerable expense and asignificant loss of electrode tip metal for RF (radiofrequency) ablationor the like. Such an approach leads to an undesirably larger tip size toaccommodate the two transducers or to poorer performing smaller(thinner) acoustic standoffs and/or backers for the dual transducers.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the present invention provide a combination catheter forforward and side lesioning with acoustic or ultrasonic lesion feedbackcapability.

In accordance with an aspect of the present invention, a system forablation with acoustic feedback comprises a catheter which includes anelongated catheter body extending longitudinally between a proximal endand a distal end along a longitudinal axis; at least one ablationelement disposed in a distal portion which is adjacent the distal end ofthe catheter body to ablate a targeted tissue region outside thecatheter body; and a pulse-echo ultrasonic transducer disposed in thedistal portion and arranged to emit and receive an acoustic beam along acentroid in a beam direction, at a transducer beam angle of betweenabout 30 degrees and about 60 degrees relative to a distal direction ofthe longitudinal axis at a location of intersection between thelongitudinal axis and the beam direction of the centroid of the acousticbeam of the ultrasonic transducer, wherein the pulse-echo ultrasonictransducer transmits and receives acoustic pulses to provide lesioninformation in the targeted tissue region being ablated. The systemfurther comprises an ablation power subsystem to provide ablation powerto the at least one ablation element; an ultrasonic transmit and receivesubsystem to operate the pulse-echo ultrasonic transducer to transmitand receive acoustic pulses; a control subsystem which includes aprocessor and one or more modules executable by the processor to controloperation of the ablation power subsystem and the ultrasonic transmitand receive subsystem; and a display to display information includingthe lesion information.

In one embodiment, the system further comprises a single packagecontaining the ablation power subsystem, the ultrasonic transmit andreceive subsystem, the control subsystem, and the display; and anoperational link coupled between the single package and the catheter. Inanother embodiment, the system further comprises: a first packagecontaining the ablation power subsystem and none of the ultrasonictransmit and receive subsystem and the control subsystem; a secondpackage separate from the first package and containing one or more ofthe ultrasonic transmit and receive subsystem, the control subsystem, orthe display; a first operational link coupled between the first packageand the catheter; and a second operational link coupled between thesecond package and the catheter. The second package is selected from thegroup consisting of a handheld device, a tablet, a flat screen, and atouch-screen device.

In one embodiment, only one of the first package and the second packagecontains the display. In another embodiment, the first package has afirst display and the second package has a second display.

In specific embodiments, the one or more modules include at least oneof: an ablation power control module to control the ablation powersubsystem to provide ablation power; an ultrasonic control module tocontrol the ultrasonic transmit and receive subsystem to transmit andreceive acoustic pulses; and a transducer detection informationprocessing module to process transducer detected information from thepulse-echo ultrasonic transducer and to provide feedback, based on theprocessed transducer detected information, to be used to monitor orcontrol ablation by the at least one ablation element. The transducerdetected information includes a detected lesion depth along a beamemanation direction. The transducer detection information processingmodule includes a lesion depth correction module which converts thedetected lesion depth along the beam direction to a corrected lesiondepth in a normal direction which is perpendicular to the tissue surfacein contact with the at least one ablation element. Processing thetransducer detection information by the transducer detection informationprocessing module comprises at least one of: determining an uncorrectedor corrected lesion depth; determining lesion-making progress;determining a tissue thickness; determining lesion transmurality;identifying activity indicative of prepopping or popping; providing anaudible feedback warning of prepopping; determining a rotation state ofthe distal portion; and determining a distance from the distal portionto the tissue surface from within a blood pool.

In some embodiments, processing the transducer detection information bythe transducer detection information processing module comprisesidentifying activity indicative of prepopping. The ablation powercontrol module is configured, in response to the identified activityindicative of prepopping, to adjust at least one of an ablation power, aduty-cycle or ramp-rate, and an ablation irrigant flow rate to reduce achance for popping. The system further comprises a user interface toreceive input from a user to be displayed or to be used for executingthe one or more modules by the processor. Only one pulse-echo ultrasonictransducer is provided in the catheter. The system further comprises amanipulation mechanism to manipulate the distal portion of the catheterbody in movement including rotation of at least the distal portion ofthe catheter around the longitudinal axis. The one or more modulesinclude a manipulation mechanism control module to control themanipulation mechanism to rotate at least the distal portion of thecatheter body.

In accordance with another aspect of the invention, a system forablation with acoustic feedback comprises: a catheter; an ablation powersubsystem to provide ablation power to the at least one ablationelement; an ultrasonic transmit and receive subsystem to operate thepulse-echo ultrasonic transducer to transmit and receive acousticpulses; a control subsystem which includes a processor and one or moremodules executable by the processor to control operation of the ablationpower subsystem and the ultrasonic transmit and receive subsystem; adisplay to display information including the lesion information; and asingle package containing the ablation power subsystem, the ultrasonictransmit and receive subsystem, the control subsystem, and the display.

In some embodiments, the ablation power subsystem comprises an RFgenerator to provide RF ablation power to the at least one ablationelement, and the system further comprises one or more electromagneticshields to prevent at least one of electromagnetic interference betweenthe subsystems within the system or electromagnetic interference betweenthe subsystems and external equipment outside the system.

In accordance with another aspect of this invention, a system forablation with acoustic feedback comprises: a catheter; an ablation powersubsystem to provide ablation power to the at least one ablationelement; an ultrasonic transmit and receive subsystem to operate thepulse-echo ultrasonic transducer to transmit and receive acousticpulses; a control subsystem which includes a processor and one or moremodules executable by the processor to control operation of the ablationpower subsystem and the ultrasonic transmit and receive subsystem; adisplay to display information including the lesion information; a firstpackage containing the ablation power subsystem and none of theultrasonic transmit and receive subsystem and the control subsystem; anda second package separate from the first package and containing one ormore of the ultrasonic transmit and receive subsystem, the controlsubsystem, or the display.

In some embodiments, the second package is selected from the groupconsisting of a handheld device, a tablet, a flat screen device, and atouch-screen device. The second package is configured to be suitable foroperation in a sterile field. The second package contains the display. Afirst operational link is coupled between the first package and thecatheter, and a second operational link is coupled between the secondpackage and the catheter.

These and other features and advantages of the present invention willbecome apparent to those of ordinary skill in the art in view of thefollowing detailed description of the specific embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of sideways ablation using an ablating catheterin a sideways manner to lesion tissue from within a blood cavity orheart chamber.

FIG. 2 shows an example of forward tip-end ablation.

FIG. 3 is a partial sectional view of an RF ablation tip having a singletransducer with an angular orientation for lesion feedback during tissueablation.

FIGS. 4( a)-(c) are partial sectional views of the ablation tip of FIG.3 showing an example of a rotation mechanism for rotating the ablationtip and illustrating lesion shapes and depths in the tissue during andafter ablation involving contact between the ablation tip and thetissue.

FIG. 5 shows a schematic block diagram of an ablation systemincorporating the acoustic feedback catheter of FIG. 3.

FIG. 6 shows a flow diagram illustrating the logic and decision-makingemployed by the hardware and software of the ablation system of FIG. 5.

FIG. 7 is a partial sectional view of an RF ablation tip wherein thetransducer itself is forward pointing but its beam is redirectedsideways by an acoustic mirror before exiting the ablation tip.

FIG. 8 is a schematic diagram showing an ablation system with acousticfeedback as a self-contained system product.

FIG. 9 shows an example of a block diagram of the control subsystem.

FIG. 10 is a schematic diagram showing an ablation system with acousticfeedback in the form of a tablet-like system control and acousticfeedback processing product coupled with an ablation power subsystemproduct.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description of the invention, reference ismade to the accompanying drawings which form a part of the disclosure,and in which are shown by way of illustration, and not of limitation,exemplary embodiments by which the invention may be practiced. In thedrawings, like numerals describe substantially similar componentsthroughout the several views. Further, it should be noted that while thedetailed description provides various exemplary embodiments, asdescribed below and as illustrated in the drawings, the presentinvention is not limited to the embodiments described and illustratedherein, but can extend to other embodiments, as would be known or aswould become known to those skilled in the art. Reference in thespecification to “one embodiment,” “this embodiment,” or “theseembodiments” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the invention, and the appearances ofthese phrases in various places in the specification are not necessarilyall referring to the same embodiment. Additionally, in the followingdetailed description, numerous specific details are set forth in orderto provide a thorough understanding of the present invention. However,it will be apparent to one of ordinary skill in the art that thesespecific details may not all be needed to practice the presentinvention. In other circumstances, well-known structures, materials,circuits, processes and interfaces have not been described in detail,and/or may be illustrated in block diagram form, so as to notunnecessarily obscure the present invention.

In the following description, relative orientation and placementterminology, such as the terms horizontal, vertical, left, right, topand bottom, is used. It will be appreciated that these terms refer torelative directions and placement in a two dimensional layout withrespect to a given orientation of the layout. For a differentorientation of the layout, different relative orientation and placementterms may be used to describe the same objects or operations.

Furthermore, some portions of the detailed description that follow arepresented in terms of algorithms, flow-charts and symbolicrepresentations of operations within a computer. These algorithmicdescriptions and symbolic representations are the means used by thoseskilled in the data processing arts to most effectively convey theessence of their innovations to others skilled in the art. An algorithmis a series of defined steps leading to a desired end state or resultwhich can be represented by a flow chart. In the present invention, thesteps carried out require physical manipulations of tangible quantitiesfor achieving a tangible result. Usually, though not necessarily, thesequantities take the form of electrical or magnetic signals orinstructions capable of being stored, transferred, combined, compared,and otherwise manipulated. It has proven convenient at times,principally for reasons of common usage, to refer to these signals asbits, values, elements, symbols, characters, terms, numbers,instructions, or the like. It should be borne in mind, however, that allof these and similar terms are to be associated with the appropriatephysical quantities and are merely convenient labels applied to thesequantities. Unless specifically stated otherwise, as apparent from thefollowing discussion, it is appreciated that throughout the description,discussions utilizing terms such as “processing,” “computing,”“calculating,” “determining,” “displaying,” or the like, can include theactions and processes of a computer system or other informationprocessing device that manipulates and transforms data represented asphysical (electronic) quantities within the computer system's registersand memories into other data similarly represented as physicalquantities within the computer system's memories or registers or otherinformation storage, transmission or display devices.

The present invention also relates to an apparatus for performing theoperations herein. This apparatus may be specially constructed for therequired purposes, or it may include one or more general-purposecomputers selectively activated or reconfigured by one or more computerprograms. Such computer programs may be stored in a computer-readablestorage medium, such as, but not limited to optical disks, magneticdisks, read-only memories, random access memories, solid state devicesand drives, or any other types of media suitable for storing electronicinformation. The algorithms and displays presented herein are notinherently related to any particular computer or other apparatus.Various general-purpose systems may be used with programs and modules inaccordance with the teachings herein, or it may prove convenient toconstruct a more specialized apparatus to perform desired method steps.In addition, the present invention is not described with reference toany particular programming language. It will be appreciated that avariety of programming languages may be used to implement the teachingsof the invention as described herein. The instructions of theprogramming language(s) may be executed by one or more processingdevices, e.g., central processing units (CPUs), processors, orcontrollers.

Exemplary embodiments of the invention, as will be described in greaterdetail below, provide acoustic or ultrasonic lesion feedback RF ablatorsand ablator tips and, more specifically, to an ablation system thatemploys an ultrasonic transducer with an angular orientation for lesionfeedback in an ablation catheter, preferably converts a detected lesiondepth from the ultrasonic transducer to a corrected lesion depth, andutilizes the lesion feedback to control and/or report the progress ofthe ablation. Two arrangements of the ablation system with acousticfeedback are disclosed. In the first arrangement, the ablation powersubsystem and the other components for system control and acousticfeedback processing are fully integrated into a self-contained systemproduct. In the second arrangement, the ablation power subsystem ishoused in a first package as a separate product from the second packagecontaining the other components.

An ideal lesion-feedback capable ablation catheter would be small insize (e.g., 7 French) and allow for lesions to be made forwardly orsideways (or in-between tip-to-tissue orientations) with the aid oflesion feedback information. In specific embodiments, a singletransducer catheter is provided for that purpose. Prior work involveddual transducers on 9 French catheters, one transducer being forwardlooking and the other one side-looking. The single acoustic transducerherein is still a pulse-echo pinger device. Dual transducers may be usedin other embodiments.

A. Ablation Catheter with Ultrasonic Transducer

FIG. 1 shows an example of sideways ablation using an ablating catheter1 in a sideways manner to lesion tissue 2 from within a blood cavity orheart chamber 3. In this mostly side-burning approach, the longitudinalaxis of the ablating tip 1 a has an approximate angle θ₁ with the tissuewall 2. The tissue contact angle θ₁ in this side-burning scenario istypically between about 0 and 45 degrees. A lesion 4 a is depicted ashaving been formed and that lesion 4 a is shown as having an approximatemaximum depth of d₁ and an approximate maximum length (along the tip 1a) of w₁. As is usually the case, the catheter 1 has a metallic orelectrically conductive ablative RF electrode tip 1 a and an extendedflexible shaft or lumen 1 b.

FIG. 2 shows an example of forward tip-end ablation. The catheter 1 isessentially the same as that in FIG. 1 but it is positioned to have atissue contact angle θ₂ that is generally between about 45 and 90degrees for forward or tip burning. A formed lesion 4 b is shown ashaving a different maximum depth d₂ and different maximum width w₂ ascompared to those dimensions in FIG. 1.

Both FIG. 1 and FIG. 2 have XYZ coordinate systems. The X-axis isparallel to the longitudinal axis of the catheter tip 1 a at azero-degree tissue contact angle, and the Y-axis is parallel to thelongitudinal axis of the catheter tip 1 a at a 90-degree tissue contactangle. In the sideways ablation case of FIG. 1, the lesion 4 a will belonger along the tip direction (w₁ direction along X-axis) than it iswide (along the Z-axis). This is simply because the tip-to-tissuecontact area is longer in that direction. In the forward ablation caseof FIG. 2, the lesion width w₂ will actually approximate a constantradius (presuming θ₂ is anywhere near 90 degrees as depicted). In anycase lesion 4 b of FIG. 2 will typically be rotationally symmetric tothe Y axis even if the lesion radius isn't constant. This is simplybecause of the rotational symmetry of the contacting tip.

FIG. 3 shows an RF ablation electrode tip having a single ultrasonictransducer with an angular orientation to its surrounding ablatorelectrode tip for acoustic lesion feedback during tissue ablation. An RFablation catheter 1 includes a distal ablating electrode tip 1 aconnected proximally to a catheter body 1 b which is flexible and hasone or more interior lumens. In this example, the catheter 1 is depictedimmersed within a blood pool 3 for forming a lesion 4 c on and into anendocardial wall 2 c of endocardial tissue 2 a. The thermal RF lesion 4c is formed on and into the tissue wall 2 c by the catheter electrode RFtip 1 a. A single ultrasonic transducer includes a piezomaterial 5 a andpreferably one or more acoustic matching layers 5 b. The ultrasonictransducer is mounted in the tip 1 a at a transducer beam centroid angleγ to the tip axis, which is between about 30 and about 60 degrees,preferably about 45 degrees (as depicted), relative to the forwarddirection of the tip longitudinal axis of the tip 1 a. The ablatingelectrode tip 1 a is typically formed, as is widely practiced, from ametal such as a platinum, gold or rhodium alloy and herein is showndrilled out or bored in order to accept the transducer and allowunobstructed acoustic beam emanation from the tip la. The acoustic beamwhich emanates has a centroid 6 and a beam envelope 6 a. The drilled outportion of tip 1 a directly in the beampath may optionally be laterovercoated with thin film electrically conductive metal such that RFlesioning still happens everywhere the tip touches the tissue 2 c.Alternatively, the bored out beampath region is not relied upon for RFablation and only the surrounding remaining tip metal still serves tocause RF ablation. Typically the tip 1 a starts as a solid cylinder ofmetal which is bored out however within the scope is a tip which startsas a tube or shell. A sheath 91 may be used to introduce the catheter 1to the target tissue region for ablation. As known in the art, thesheath 91 is typically made of a polymeric material and may be braided,and may be steerable or non-steerable. As discussed below, the catheter1 may be rotated relative to the non-rotating sheath 91 which serves toprotect the patient's lumen such as an artery or vein duringintroduction and/or rotation of the catheter 1.

The entire catheter tip 1 a is further depicted having a presentation totissue angle (tissue contact) of θ₃ relative to the endocardial wall 2c, which is horizontal along axis X in FIG. 3. The transducer 5 a/5 bemits and receives outgoing and incoming reflected acoustic pulsestraveling at the tissue's approximate sonic velocity of 1540 meters/secalong a beam axis 6 within a beam envelope 6 a. The transducer 5 a/5 b,as is customary, is mounted on an acoustically attenuative backermaterial 5 d. The acoustic waves travel through the lesion 4 c outwardsand then back inwards as they are reflected from various depths inaccordance with lesion induced damage and microbubbles at each suchdepth. The lesion 4 c has a depth d₃ measured along the acoustic beampath 6 which just happens to also be the maximum penetration depth ofthe lesion into tissue 2 a for this particular tip θ₃. Note that forrandomly chosen tip-to-tissue angles the “detected” acoustic depth willnot be “straight into” the tissue and therefore may somewhat differentthan the actual maximum “straight down” depth. Again we emphasize thatthe beam envelope 6 a typically has a finite width which converges ordiverges with distance from the transducer, but the beam will alwayshave at least one centroid 6 or central angle or sort of centerline withan angle γ to the local axial tip axis. This centroid may be defined inany conventional manner such as its being an axis of beam symmetry or anaxis of peak intensity.

B. Acoustic Measurements and Lesion Depth Estimation

FIG. 3 shows an underlying untargeted tissue layer 2 b under the tissuelayer 2 a to be ablated. This is to call attention to the fact that thetransducer 5 a/5 b may also detect interfaces such as the 2 a/2 binterface. A likely real example would be endocardial tissue 2 a andunderlying pericardial tissue 2 b. As the heart oscillates and the bloodsurges there through, there usually is a heartbeat-time angularexcursion of the tissue contact angle θ₃. By time-sampling the pingeddepths across multiple heartbeats and knowing the tip-to-tissue contactangles, one can determine the shortest distance (true local thickness)of layers such as 2 a/2 b by simple trigonometry. That information canbe utilized to compute a degree of transmurality of the lesion 4 c inlayer 2 a or to determine a safe distance from an esophagus, lung oraorta 2 b to be avoided, for example.

Furthermore, one may utilize transducer pinging to monitor the approachof the catheter tip to the wall 2 c from within the blood pool 3 or todetect incipient (inaudible prepops) or actual steam pops and avoidlarge pops by throttling back or shutting off ablation power and/orincreasing nearfield cooling irrigation. One may also deduce the angleof the tip relative to the wall before contact since the tip motionsprovide some angularly swept data; however, in a preferred approach asdiscussed below, techniques involving the use of navigational systemssuch as Ensite™ or Carto™, or the use of X-ray or the like can beutilized to obtain tip angle θ₃ to tissue surface 2 c.

It will be appreciated that if γ and θ₃ are both 45 degrees, then thebeam 6 a of the transducer 5 a/5 b will be oriented normally or at 90degrees into the tissue wall 2 c (along the −Y axis) in FIG. 3. Moretypically though, γ will be fixed at an angle of about 45 degrees(typically between 30 and 60 degrees) and θ₃ will be variable throughoutan ablation procedure and will depend on how the catheter tip la ispresented to the tissue wall 2 c by the practitioner for that particularlesion. The presentation angle of the electrode tip 1 a to tissue θ₃ canphysically be from about 90 degrees (tip-normal) to about 0 degree(tip-parallel) depending on the particular lesion being made. Anablation procedure may involve multiple lesions made at differentcontact angles. The tip may also be dragged during ablation as is knownand the inventive feedback likewise gathered during suchablating/dragging.

Before proceeding note that in FIG. 3 the depicted lesion depth d3 isthe maximum penetration depth of the lesion 4 c measured orthogonal tothe tissue surface 2 c. If the lesion 4 c is not hemispherical (i.e.,not constant radius) in volumetric shape, then any different d measuredalong a beamline 6 which is not orthogonal into tissue 2 c will have adepth (or radius) different from d-max. Practitioners are interested ind-max because it is the indicator for transmurality through the targetlayer 2 c (the deepest lesion penetration). Most real lesions, dependingon the tip angle θ₃, will have fairly reproducible nonhemisphericalshapes if not asymmetric shapes. Knowing this, one can either (a) usethe non-orthogonally detected d as an approximation of d-max, or (b)utilize lookup tables or mathematical models of lesions, wherein basedon a given depth (radius) along a first direction, one can compute thedepth along a second direction (e.g., the orthogonal d-max direction).For maximal convenience, these models can utilize lesions of constantshape (fixed aspect ratios) which simply grow or scale in absolute sizeat those fixed ratios. In the unique case where the tissue contact angleθ₃ is 45 degrees and the transducer 5 a/5 b is also mounted in the tip 1a at 45 degrees (γ=45 degrees), the pinged lesion depth d₃ is the actualtissue-orthogonal maximum penetrating lesion depth d₃ (because thetransducer 5 a/5 b is orthogonal to the tissue 2 c) and the maximumdepth typically occurs directly or nearly directly under the most deeplytissue-indenting contacting tip portion. However, presuming thetransducer angle γ still is equal to 45 degrees (the same catheter) butthe tissue contact angle θ₃ is reduced to 30 degrees (from 45 degrees),the beam 6 centroid is no longer normal to the tissue 2 c but is noworiented 15 degrees to it (not shown). If one knows the tip-tissuecontact angle and has the lesion model for that tip angle then themaximum actual depth is easily computed by scaling the model to have thedetected dimension along the detected direction and computing the depthalong the orthogonal direction using the scaled model.

For a catheter tip 1 a embedded, indented or depressed into a tissuesurface 2 c (as shown in FIG. 3) and for a reasonably wide range ofangles θ₃ (the variable tip tissue contact angles), the detected lesiondepth d₃ is an approximation of the maximum depth when γ (the fixedtransducer angle) is fixed somewhere between about 30 and 60 degrees(preferably at about 45 degrees). Practitioners are typically interestedin the maximum lesion depth for transmurality and in the lesionwidth/length insofar as being able to say adjacent lesions arecontinuous or abutted or not. Thus, depending on the required accuracy,the practitioner may want to utilize an inventive device having trued-max computation or lookup capability using the above-describedangle-detection and lesion models.

The ablative tip 1 a has an axial length of L and a diameter D. For a 7French tip, D is 7/π or 7 French divided by 3.1416 (just over 2 mmdiameter). The tip length L will typically be in the range of about 2Dto 6D presuming a rigid tip. 7-French devices are preferred for manyablations; however, the inventive devices may comprise any smaller orlarger French size desired (e.g., 5 or 6 or 8 French).

Despite this fairly good depth approximation capability, it is actuallypossible to do even better if one knows the actual real-time tissuecontact angle θ₃ at the moment of measurement. In that case, one canapply a correction factor, if worthwhile, to account for differencesbetween the detected depth and the actual maximum depth based on benchstudies done using that tip orientation. This correction factor correctsfor the fact that the “depth” measured along the acoustic beam line willtypically be slightly non-normal to tissue and may report a “depth”which is actually larger for flat pancake lesions (or even smaller fornarrow deep lesions) than the real 90 degree penetration depth.

The tissue contact angle θ₃, if it is desired for the most accurateresult, can be determined or deduced in one or more of several ways andsome of the more likely methods are described. While a useful product isreadily possible even without such correction factors, a premium productmay include the correction factor capability. Tissue contact angle (θ₃)detection methods include the following three approaches.

(1) The first is θ₃ from an Ensite™(http://www.sjmprofessional.com/Products/US/Mapping-and-Visualization/EnSite-System.asPx)or Carto™(http://www.biosensewebster.com/products/navigation/cartoxp.aspx)cardiac spatial navigation system based on computed or estimated tipangle to the graphically modeled endocardial surface. These systemsalready create three-dimensional (3-D) graphical displays of cardiacstructures and arrhythmias and enable the spatial navigation ofelectrophysiology catheters in real time. Such systems already visuallyand mathematically provide the spatial orientation of the electrode tipand the spatial map and shape of the heart/tissue wall. By either simplyobserving the display where the RF electrode touches the wall andvisually estimating the angle or by adding a simple angle computationutilizing the tip orientation and a computed local wall tangent derivedfrom the wall model, one could obtain the tissue contact angle θ₃.

(2) Most modern catheters have radiopaque markers of gold or other heavymetal routinely used to discern in X-Ray fluoroscopy the position andorientation of a catheter tip such as 1 a and sometimes even of aflexible lumen portion such as 1 b. Using such conventional markers, theuser can already visually discern the approximate tip orientation withrespect to the contacting tissue and hence estimate the angle θ₃. As isalso widely known, one may additionally utilize an X-Ray contrast agentreleased into the blood from the catheter to enhance the outline of theblood filled chambers and the heart wall.

(3) The third is the angle θ₃ estimated from a force/angle sensor suchas an Enclosense™ force/angle sensor (www.enclosense.com). Such cathetertips as that of Enclosense's “Tacticath”® already report their contactangle and contact force for other purposes of obtaining reproducibleablations. By mounting our inventive transducer in such a tip, onethereby obtains the tissue contact angle θ₃ as well as the tip contactforce.

The actual tissue contact angle θ₃ may be used to correct the ultrasoniclesion depth measurements but it is not always required. FIG. 4 is usedto illustrate the reason a correction may be beneficial for maximumlesion-depth accuracy. FIG. 4( a) is a partial sectional view of theablation tip of FIG. 2 showing an example of a rotational mechanism forselectively rotating the ablation tip itself and illustrating lesionshapes and depths in the tissue during and after ablation involvingcontact between the ablation tip and the tissue. In FIG. 4( a), thecatheter tip la is oriented at about 90 degrees to the tissue surface 3b. The transducer 1 c/1 d and ultrasonic beam path are thereforeoriented at about 45 degrees to the tissue surface 3 b. The tissue isalso typically somewhat indented by the pressing catheter tip 1 a. Alesion 3 a of depth d (measured in the indented state) as measured alongthe beam line has been formed by the tissue indenting tip. It will beapparent that, due both to the recovery of the indentation after the tipla is physically removed and the lesion's not necessarily having aconstant radius (even as indented), the resulting recovered tissuelesion may have a shape ranging between hemispherical (FIG. 4( b) havinglesion 3 a′) and a flattened pancake shape (FIG. 4( c) having lesion 3a″), for example. However we can generally describe the lesion inspherical or polar coordinates as having a variable radius which is afunction of at least one angle α measured with respect to a firstreference line on the tissue surface 3 b (line on paper in FIG. 4( c)),i.e., r=f1(α), as seen in FIG. 4( c). For a hemispherical lesion, theradius is r=constant. Lesions made near 90 degrees (FIG. 4( a)) aretypically bodies of revolution and rotationally symmetrical to the tip 1a, whereas if the tissue contact angle θ₃ leans over more toward 45degrees or less, the lesion starts to become more asymmetrical and nolonger a body of revolution as the tip sidewall also starts ablatingtissue as well as some of the tip end. By making lesions at varioustissue contact angles θ₃, RF powers, times, and irrigant flow rates inthe engineering development phase, one can determine the function f1(α)(FIG. 4( c)) for each such set of conditions. Such shape and sizebehavior data may be provided in or to the ablation catheter from lookuptables or by computational models operated resident on the ablationconsole or on a network, for example. Note that for an asymmetricallesion, the lesion radius sampled across the orthogonal lesion lengthand width cross sections respectively will be a function of two anglesf3(α, β), wherein β is measured with respect to a second reference lineon the tissue surface 3 b which is perpendicular to the first referenceline (line into paper in FIG. 4( c)). We have already mentioned abovethat for maximal convenience, the lesion models can be saved asapproximations of the lab data having constant aspect ratios whoseoverall size is scaled.

We show a 45 degree γ (transducer to tip angle) in FIG. 4. We show a θ₃(tip to tissue angle) of about 30 degrees in FIG. 3 and 90 degrees inFIG. 4. The actual ultrasonic beam tissue penetration angle (actualtissue beam angle) relative to the tissue normal (ignoring signs) inFIG. 3 is about 15 degrees off normal (90−45−30=15) and in FIG. 4 isabout 45 degrees off normal (90-45−90=−45).

Knowing the tissue beam angle (relative to the tissue normal) through alesion made with a known tip orientation allows, based on prior lesioncharacterization during product development, the reporting of lesionradius or depth across the two orthogonal planes or sections f1(α) andf2(β). It will be appreciated that f1(α) and f2(β) are generally similarfunctions for the depicted 90 degree lesion of FIG. 2 but can bedissimilar functions or asymmetric for an ablating tip 1 a at a lowerthan 90 degrees acute angle, as would be anticipated for an RF electrodemaking a “somewhat sideways” lesion in FIG. 1. It will further berecognized then that even when the tip 1 a takes various angles to thetissue surface 3 b in FIG. 4, as long as one knows the tissue contactangle θ₃, then one can compute or “look up” the maximum penetratingorthogonal depth of that lesion using f1(α) and f2(β) even though it maylikely not occur directly in front of the transducer. Given theultrasonically measured depth d along the angle α in FIG. 4 c and theknown tip orientation, one can compute the maximum lesion depth d-maxusing f1(α) and f2(β) and can also report its length, width, and/orvolume. That is because we know at least one detected d along abeamline, know the angle of the beamline (which gives a specific f(α, β)for that setup), and thus one can use f(α, β) and d to compute themaximum depth d-max at whatever angle it occurs as characterized in theengineering lab and provided as computational models and/or lookuptables. Essentially one plugs d into f(α, β) which scales the model tothe right size and then reports d-max (at the different angles whered-max is known to occur from prior characterization). Again, weemphasize that these corrections are to obtain maximal accuracy and arenot always necessary.

FIG. 3 shows that the transducer 5 a/5 b is stood-off from the deformedor indented tissue wall 2 c by an acoustic standoff 5 c which is alow-loss acoustic window material 1 such as urethane, TPX, polystyrene,Ultem® (an unfilled polyetherimide), silicone, or even water or blood.The standoff material fills a cavity 5 c having a length s, and may alsoserve a focusing function in the known manner if desired (i.e., anacoustic lens). This standoff 5 c allows detection of shallow lesions ofsmall depth d (e.g., in the 1 mm depth range or less) close to thetransducer face despite known nearfield acoustic reverberations oftissue contacting transducers. Further, the transducer 5 a/5 b isacoustically and mechanically backed by an acoustic attenuation backermaterial 5 d as is known for good quality pulse-echo transducers. Highacoustic impedance backers typically contain epoxy or rubber andtungsten while low acoustic impedance backers typically contain epoxyand alumina or glass filler. Either would be highly attenuative as isknown in the art, thereby attenuating the backwards propagating waves byabout 20-40 dB. The backer material is placed in a cavity 5 d, which maybe filled with at least (a) an attenuative backing material, andpossibly also (b) an electronic circuit such as an amplifier or matchingcircuit, and/or c) a sensor such as a temperature, spatial positioningor force sensor. The cavity 5 d has an angled outer surface (relative tothe transducer beam axis 6 and this also favorably discourages multipleacoustic reverberations in the backer material. Thus, the attenuativebacker material preferably has a shape conducive to reflectionminimization in addition to being an attenuative material.

As mentioned above, the transducer typically and preferably has at leastone acoustic matching layer, and at least one acoustic backer materialentity. The transducer may utilize at least one of: a single crystalpiezomaterial, a polycrystalline piezomaterial, a compositepiezomaterial, a CMUT (capacitive micromechanical ultrasound transducer)or other MEMS (microelectromechanical systems) based transducer, and apiezopolymer as is known in the transducer arts. The ultrasonictransducer typically operates somewhere in the range of about 3megahertz to about 60 megahertz, preferably about 6 megahertz to about40 megahertz, and more preferably about 8 megahertz to about 25megahertz. The transducer may have a natural focus distance withoutusing any acoustic lens. Alternatively, an acoustic lens such as aspherical lens (or an acoustic focused or unfocused mirror) is providedfor the transducer in the tip. As a lens example, the standoff in FIG. 3could also act to focus or defocus the beam as long as the materialmaking up the standoff has a velocity different from the velocity of thetissue and the interface between the lens/standoff and the tissue iscurved as shown. For instance, a low attenuation unfilled epoxy couldserve as both a curved lens and a standoff, as is widely known in theart. An acoustic mirror may be used which merely changes the directionof the beam before tip emanation or both reflects/redirects the beam andfocuses/defocuses the beam by being a curved mirror. The beam angle γ isthat to the longitudinal tip axis regardless of whether a mirror is usedto redirect the beam or not. Further examples include any lens causingthe acoustic beam to have a desirable divergence or convergence angle orcollimated zero-divergence/convergence angle, and any mirror at leastredirecting the beam and possibly also, via use of a shaped nonflatmirror, causing the acoustic beam to have a desirable divergence orconvergence angle or collimated zero-divergence/convergence angle.

As seen in FIG. 3, the transducer 5 a/5 b is emitting and receivingpings and echoes therefrom and thereto along the beam axis 6. As isknown for small disc transducers such as the one shown, there may be anatural focus at 6 a even without the use of an acoustic lens 5 c. Itwill be appreciated that the acoustic transmit/receive beam directedalong the beam axis 6 will always penetrate lesions made substantiallysideways (such as lesion 4 c in FIG. 3) as well as lesions madeforwardly (see, e.g., FIG. 2) provided the transducer beam axis 6 isrotated toward the tissue surface 2 c about the tip long axis.

The transducer mounting angle γ relative to its immediate surrounding RFelectrode 1 a is typically fixed, such as at the approximate 45 degreeangle as shown in FIGS. 3 and 4 for the rigid metal electrode tip 1 a.In some embodiments, while the electrode tip 1 a is preferably rigid inthe region immediately around the transducer, the remaining portion ofthe tip 1 a may be flexible, preferably bendably and/or axiallyflexible. This can be achieved, for instance, by lasering an array ofcircumferential or helical slots into the walls of a hollow tubularmetal tip. See, e.g., U.S. Patent Application Publication No.2010/0152731. The transducer herein could be placed, for example, at theend of such a flexible metal ablator tip, thereby allowing tip-bendingto reorient the transducer relative to tissue (and relative to thecatheter body lumen 1 b) while still being fixed relative to itsimmediately surrounding preferably inflexible tip portion.

The transducer is used to make any one or more of the following acousticmeasurements along and/or from the direction of the beam: lesion depthalong the beamline, proximity to target tissue from a blood poolstandoff position, detection of prepopping and popping relatedphenomenon, and detection of or proximity to anatomical targets to beavoided. As explained the measurement may then optionally be correctedusing models or look-up tables and a known tip/tissue beam contact anglefor maximal accuracy. The ultrasonic transducer can be operated while RFablation is active or inactive but preferably the transducer operatesduring multiple very short pauses in RF ablation (i.e., pinging isinterleaved with ablation). “Very short” means short enough thatsignificant tissue cooling does not occur, such as for pauses on theorder of milliseconds to a fraction of a second. Typically tens if nothundreds or thousands of acoustic feedback detections are made over theperiod of a heartbeat. Some may be repeated to reduce signal noise. Inone preferred case, ultrasonic measurements are time-interleaved withperiods of RF ablation so as to monitor real-time ablating action whilealso avoiding RF ablation interference into the acoustic measurements.One may also or alternatively carry out before-lesioning andafter-lesioning measurements to establish a reflection baseline or tolet microbubbles in the nearfield which limit ultrasonic penetration tonaturally be reduced upon cooling. In specific situations, at least oneacoustic detection is made in a timed relationship with a heartbeat orECG signal. That is to say, for example, ultrasonic measurements aredone preferably at least at the same phase point in the heartbeat forall heartbeats. Similar synchronized measurements may also be done atother cyclic phases of the heartbeat and/or the breathing pattern.During a given heartbeat cycle when tissues are moving, the tip-tissuecontact angle θ₃ and tip contact force will cyclically vary and angularvariation can be taken into account by recognizing that the varyingangles result in slightly different detected depths for each suchinstantaneous orientation.

The duty cycle of the ultrasonic transducer's operation is preferablyless than about 20%, more preferably less than about 10%, and mostpreferably less than about 5%. In one embodiment, the on-time for anindividual ultrasonic measurement period is equal to or less than athermal time constant of the cooling tissue which assures that onlyminimal cooling takes place between the RF power-off and following RFpower-on events. In other embodiments, the ultrasonic on-time ispreferably less than about 0.15 seconds or 150 milliseconds, morepreferably less than about 0.10 seconds or 100 milliseconds, and mostpreferably less than about 0.05 seconds or 50 milliseconds perindividual measurement period during which one or more pulse-echo eventstake place.

The catheter body and/or tip may further include any one or more of thefollowing known components: a thermistor or thermocouple, an irrigationand/or suction lumen, a spatial position sensor (as for the priormentioned Ensite™ or Carto™ systems), a contact-force sensor, part orall of a tip contact angle to tissue sensor of any type, a platinum,gold, or rhodium metal or alloy electrode component or radiopaquemember, and a metallic thin film or mesh electrode in an acousticpulse-echo path. The thin film or mesh allows the face of the transduceritself to also optionally act as an acoustically transparent yetelectrically ablating RF electrode.

A solid metal RF electrode tip 1 a would be drilled out or otherwiseprovided with a bore to allow beam passage and placement of thetransducer and the optional window, lens or standoff. If the standoff iselectrically insulating, then that portion of the tip will not cause RFablation unless it is overcoated with a metal film or foil. Within thescope of the invention is the provision of a metal coated or otherwiseelectrically conductive ultrasonic component(s) such as the standoff,lens, or matching layer such that this drilled-out region still iscapable of delivering RF ablation power even across the face of theunderlying standoff and/or lens. The inventors have found that even ifthe acoustic element face is not providing RF ablation, the nearbyremaining tip metal periphery still forms a lesion similar to that of astandard non-drilled tip. The inventors believe that this is because aslong as one has a circular donut-shaped electrode contact area totissue, the RF current density at any appreciable tissue depth isrelatively unchanged from that of a solid electrode. The tissue close toand immediately in front of the electrically insulating standoff/lens 1e is backfilled and sideways-filled with heat generated deeper in frontof the tip and adjacently at the metallic periphery of the metallic holein the tip. The astute reader will recognize that if the RF ablationelectrode and the matching layer are electrically connected and bothconductive, then the operation of the transducer and the operation ofthe RF ablation are no longer independent. Although we do not intend toteach specific electrical circuits, it will quickly be recognized thatone can simply short the transducer across its thickness during RFablation using a switch at the handle end of the catheter. That preventsthe transducer from interfering with RF power delivery and likewiseprevents transducer operation causing ablation electrode excitation.

The inventors have also found that by placing the thin metal film overthe acoustic element to also provide RF ablation from the beam emissionarea, they can reduce the maximum RF power density otherwise occurringat the peripheral circumferential edge of the cored electrode whichinhibits early bubble formation.

The RF ablation catheter has a single ultrasonic pulse-echo transducerin the RF ablating tip used for pulse-echo lesion feedback. Thetransducer beam's centroid is oriented at approximately 30-60 degrees tothe catheter tip longitudinal axis such that it has at least some viewof lesions being made in any FIG. 3 catheter-to-tissue orientation θ₃.If the ultrasonic beam, for example, has a somewhat diverging beamwithin the lesioned region, then it “covers” a wider range of anglesthan a narrower beam for given transducer angle γ and tissue contactangle θ₃ and will report an average lesion depth d₃ for that divergentangle range presuming no effort is made to discern the closerreflections from the deeper reflections. We again stress that the 30-60degrees is the beam emanation angle relative to the surrounding tiplongitudinal axis regardless of whether the transducer is used with orwithout an acoustic mirror which internally redirects the beam beforetip emanation.

The catheter 1 (or the catheter tip 1 a alone in FIG. 4 a) is manuallyor automatically rotated about the longitudinal tip axis such that thetransducer beam faces the indented tissue 3 as directly (as near normal)as possible for measurement of the lesion depth d along the beam. Thisorientation also typically results in the maximum acoustic reflectedenergy from depth and the maximized signal/noise performance.Alternatively, one may measure the depth d at a variety of tip-to-tissueorientations during or after local lesioning is tentatively finished.

Referring again to FIG. 4( a), the electrode tip 1 a may be rotatedrelative to catheter body 1 b such as upon a bearing member 1 j. Arotational drive shaft 1 l is used to rotate around the longitudinalaxis in an axial rotational direction 1 m to impart rotation 1 k uponthe tip 1 a relative to the nonrotating catheter body 1 b. The driveshaft 1 l could be replaced with an in-tip motor or some other in-tippowered actuator. Alternatively, and as widely known in the rotationalcatheter art, one may bodily rotate the entire catheter 1 a/1 b whereinthe tip 1 a does not rotate relative to the body 1 b but is fixedrelative to the body 1 b. Such bodily rotation is now routinely done bythe practitioner manually rotating a rotational control member 11 of aproximal catheter handle 12. As is also known, catheter 1 may be bodilyrotated in that manner while residing in a stationary introducersurrounding sheath 91 which provides a slippery bearing surface aroundthe catheter 1 and may have its own steering wires. An advantage of theapproach using the rotational bearing 1 j of FIG. 4( a) is that one getsrotation without requiring a larger overall catheter or catheter/sheathdiameter or French size. If one instead (or in addition) uses thesheath, then one now is introducing a larger sheath into the lumen andmay be more restricted in access. However, the inventors have had goodresults using a 7 French ablation catheter in sheaths designed to acceptthe 7 French ablation catheter.

An important aspect of the present invention is that a lesion's shapeand specific size (actual depth and aspect ratios) are primarily afunction of power, cooling, force, and contact angle. In general for agiven set of these parameters, one obtains highly similar lesions interms of their three dimensional shapes (i.e., aspect ratios) even astheir absolute sizes increase during growth. The pinger transducer 5 a/5b of FIG. 3 provides the actual instantaneous lesion depth along beamaxis 6 regardless of how the parameters are set. Given the beam axisactual “lesion depth” from the transducer which in general is not 90degrees to the local tissue, the following summarizes the threeabove-described examples of how to estimate the actual maximum lesiondepth roughly orthogonal (i.e., 90 degrees) to the compressed contactedtissue centroid point. First, as a rough estimate, one can simply usethe uncorrected beamline depth as an approximation of the lesion's trueorthogonally penetrating d-max. Second, as a finer estimate, one canutilize the practitioner's estimate of actual contact angle such as thatdetermined by fluoroscopy or the like. This might even be done withautomatic feedback from the x-ray equipment. Knowing the angle and anyinformation relating to how depth varies by angle for particular lesionsituations (such as with a lesion model for the given contact angle),one can correct for the orthogonal maximum depth. Third, a preferredapproach utilizes the tip contact angle feedback as provided by a 3Dchamber modeling and navigation system, such as the Ensite™ products ofSt. Jude Medical and the Carto™ products of Biosense Webster. This couldbe done transparent to the practitioner. This third approach canactually utilize data from any available angle-sensing sensor onboardthe tip, not just the graphical based systems mentioned. This lesiondepth correction is performed by a lesion depth correction moduledescribed below (see FIG. 5).

The basic steps for true 90 degrees-to-contacted tissue lesion depthd-max determination are as follows: (a) obtain before and afterlesioning pinged echoes (which may also include interleavedmeasurements); (b) looking at differences in the pinged echoes aslesioning proceeded (or has tentatively finished), determine theprojected lesion depth d-beamline along the pinger beam axis 6 of FIG.3; (c) do one of the following: (i) assume a nominal contact angleestimate or measure a contact angle using imaging means such asfluoroscopy as described above, (ii) automatically compute a contactangle using a 3D navigation/chamber modeling system as described above;and (d) report (or provide feedback regarding) the actual maximum lesiondepth d-max orthogonal to the contacted tissue surface which is obtainedvia a model of a typical lesion made under those conditions (at thatcontact angle) wherein d-beamline is employed to scale the fixedproportions model to the correct size and then d-max is computed andreported at its known orthogonal position using the scaled model.

C. Ablation System with Acoustic Feedback

FIG. 5 shows a schematic block diagram of an ablation systemincorporating the inventive acoustic feedback catheter and supportinghardware and software. The major components include ablation logic unit8 a, ablation power unit 8 b, pinger send/receive power/logic unit 9,GUI, CPU, software, firmware, storage and networking unit 10, andablation catheter with sensing transducer 11, optional 3Dnavigation/modeling system unit 12, optional catheter manipulation robot13 a/b, and a variety of lines 13 for passage of data, power, logic,coolant, and the like.

The ablation logic unit 8 a includes logic circuitry to power andcontrol ablation, which can be TTL (Transistor-Transistor Logic), gatearrays, or even software. The ablation power unit 8 b includes theactual power source for ablation. In addition to RF, other ablationenergy sources may be employed including lasers, cryo, RF bipolar, RFunipolar, microwave, HIFU (High Intensity Focused Ultrasound), andelectroporation. Such power supplies are usually accompanied by a supplycooling mechanisms. The pinger send/receive power/logic unit 9 includesthe pinging transmit powering and receiving circuitry and logic for thetransducer pinger. On the transmit side it is capable of sending shortpulses or pulse trains at an operating frequency. On the receive side itsenses the voltage waveforms induced by returning echoes, possiblyincorporating amplification, noise reduction, and electrical-matching.

The GUI, CPU, software, firmware, storage and networking unit 10 is alsoreferred to as the control and interface system 10. It includes agraphical user interface (GUI), firmware for system operation,storage/memory for system operation, and networking interfaces. The GUImay include any one or more of a display, a touch screen, a keyboard, acomputer mouse, and the like. If the optional robotic subsystem 13 a/band/or navigation system 12 are also employed, then the user GUI may beused on those subsystem(s) as well. Software in the ablation system canrun on the CPU in the control and interface system 10; however, someamount of software/firmware may also be distributed within theindividual modules or units in the ablation system of FIG. 5. Patientinformation is stored in the storage/memory and a network interface tothe hospital network is provided in the control and interface system 10.The control and interface system 10 is configured or programmed toprocess transducer detection information from the pulse-echo ultrasonictransducer and to provide feedback to a user via the GUI and as internalsystem feedback to be used to control ablation by the ablation tip. Thecontrol and interface system 10 includes a lesion depth correctionmodule 10A, in the form of hardware or software or firmware, forperforming the lesion depth correction described above, to convert thedetected lesion depth along the beam direction to a corrected lesiondepth in a normal direction which is perpendicular to the tissue surface2 c in contact with the ablation tip 1 a. The control and interfacesystem 10 is coupled to the rotation mechanism to rotate the distal tippreferably in order to achieve as near an orthogonal tip-to-tissuecontact as possible. The control system 10 may also include prepop orpopping detection software. During lesioning, the inventive system mayalso supplement the acoustic feedback with known electrical impedancefeedback or ECG feedback (not shown) for even better control.

The ablation catheter with sensing transducer 11 includes, preferably, adisposable acoustic feedback ablation catheter with the pingertransducer such as that shown in FIG. 3 or 4. This invention is notlimited to the single transducer shown in FIG. 1, but may provide dualtransducers or the like. The ablation catheter 11 may also include oneor more of a variety of known sensors 11 a that may be resident in/on orcoupled to the ablation tip, such as temperature sensors, tip-rotationsensors, tissue contact force or angle sensors, blood flow or pressuresensors, IVUS or OCT imaging transducers or elements and navigationsensors. The inventors have herein described the single transducer ashaving a fixed angle γ (FIG. 3). Within the scope of “fixed angle” is arotating transducer or transducer tip (such as that of FIG. 4 or of arotating IVUS transducer) wherein the transducer is rotated about thetip axis manually, automatically, intermittently or continuously therebyproviding measured depths d-beamline over a range of angles. It will beappreciated that those angles relative to the tip longitudinal axis arealso in a fixed relationship. We again mention that the ablationcatheter may be employed from within a sheath 91 such as a steerableAgilis™ sheath.

The optional 3D navigation/modeling system unit 12 includes, forexample, the Ensite™/NavX™ system from St. Jude Medical or the Carto™system from Biosense-Webster for 3D spatial navigation and/or surfacemodeling. It is capable of automatically calculating and providing thetransducer tip contact angle to tissue utilizing system software withoutuser involvement. Alternatively the contact angle can be eyeballed fromthe navigator GUI. The optional catheter manipulation robot 13 a/b is arobot which can manipulate the catheter 11 thus reducing x-ray exposureof the practitioner or allowing for remote procedures. The lines 13allow passage of electrical power, data, logic signals, ping receivesignals, ping transmit signals, and any required coolant between thevarious system units and/or catheter.

FIG. 6 shows a flow diagram illustrating the logic and decision-makingemployed by the hardware and software of the ablation system of FIG. 5,which depicts a functional block diagram of a representative physicalsystem implementation. The major sections of the diagram are a setuploop (upper loop blocks 20-24 and 32) wherein the user inputs theablation parameters and selects an ablation site and a lesioning loop(lower loop blocks 25,26,27,28, 30, 31) wherein the ablation is carriedout with an awareness of pinging feedback. Specifically, a start block20 is where a user inputs one or more requested lesion parameters suchas one or more of a lesion dimension or volume, an RF power or time, amaximum temperature, or an irrigant flow rate. At the same time, atblock 20 the catheter model number is manually or automaticallyinputted. At the same time, the system itself receives from block 32 anyavailable tip contact angle, contact force, contact impedance and lesionmodels.

At block 21, continuous pinging begins and at subsequent block 22 (takeecho sample(s) N) and block 23 (establish baseline (pre-lesioning)), thepinger is continuously operated while the doctor chooses a lesioningtarget. At block 24, the pinging echoes are analyzed and reported suchas to carry out any one or more of (i) warning of in-range interfacesand (ii) advising that tissue contact is good or bad. Subsequently, theuser gives the go-ahead for lesioning or commands the system to stopsuch that setup can be repeated at block 20 at a different site orcoupling/contact situation.

Presuming the user or doctor gives the go signal at block 24, thebaseline prelesion pinged echo from the intended target site is saved atblock 24 as a starting reference for later comparison before proceedingto block 25. At the next block 25, ablation begins with the inputtedsettings of block 20 (e.g., nominal settings such as power, time,temperature, and irrigant). The next block 26 depicts pinging for lesionprogress monitoring, the pinged data results then being employed infollowing block 27 to determine a lesion state and/or pop risk. Then,block 28 evaluates whether any power, flow or other lesioning parametersshould be adjusted (automatic modifications to user-set parameters)depending on whether the lesion state of block 27 was determined ason-plan or safe or as off-plan or unsafe. Next, block 30 shows suchadjustments (if any) being applied followed by a subsequent return toblock 26 for continued progress pinging under the adjusted lesioningparameters. As an alternative to applying adjustments at block 30, thesystem may determine that an emergency shutdown is necessary at block 29because no adjustment can recover the desired behavior; however, thisoutcome is preferably avoided by having the feedback and adjustmentsdiscussed above. We note that the lesioning loop may be passed throughdozens or hundreds of times during an ablation.

The lesioning status is thus reported both to the system itself (block27 to 28) and to the GUI (block 27 to 31). Note that the optionalsources of contact angle, contact force, contact impedance andlesion/prepop models of block 32 may also be provided to block 27 duringlesioning if they have changed.

The inventors note that it is preferable to ping at least every secondor so if not much more often (but still at the low duty cycle discussedpreviously) so as to avoid having the system being surprised by a largeor unsafe change in lesion progress or pop risk. In particular we knowthat changes to lesioning parameters at block 28 must be applied asearly and as often as possible so as to avoid ever getting into aserious pop state. The “algorithm” is software (or firmware) appliedparticularly at blocks 27 and 28 which is used to (a) quantify a lesionstate and/or a pop risk and (b) compare it to a desired state and/orrisk and make ablation adjustments if needed such as an ablative powerreduction. Such algorithms can take several forms. Two preferredalgorithm features are discussed herein below.

The first feature is a pop avoidance portion of code which essentiallylooks for excessive ping reflections or excessive ping reflection growthrates in the lesioning field, but most particularly in the 1-3 mm rangewhereat the hotspot is known to occur for irrigated RF catheters.Reflected echoes are caused by both microbubble formation in the tissueand by actual protein cross-linking of the tissue. The inventors havefound that when an undesirable nearfield hotspot prepop bubble cloudgets dense enough (acoustically opaque), one can no longer see echoescoming from behind it (from deeper). This is a sure sign of a potentialpop and what needs to be done is to reduce the temperature increase rateand peak temperature otherwise reached in the prepop region. That can bedone, for example, by throttling RF ablation power (on/off, proportionalcontrol etc) and/or by increasing irrigant flow at blocks 28/30.

The second feature is a lesion progress portion of the code which looksfor a minimum desired strength of reflection from tissue thought to beindicative of complete lesioning or necrosis. That is, the looked-forlevel of pinged reflection is reached when a microbubble or othercontrast has increased to a level known (via engineeringcharacterization during product development) to correlate to fullylesioned or necrosed tissue. Lower levels indicate partially lesionedtissue. For example, fully lesioned tissue might have a reflectivity 20,30 or 40 Db above the prelesioned level at a particular depth. Anotherway to state this is that one looks for what portion of the ingoing beamis reflected from which depths. Higher reflections indicate morelesioning damage. For example, if half or three quarters of the ingoingbeam is newly reflected after some lesioning from a distributed depth,then it will be obvious that substantial reflectors indicative ofmicrobubbles and protein-crosslinking have occurred through adepth-range and that the strong reflection is not just a localized (indepth) prepop bubble cloud. It should be apparent that by establishing aping prelesion baseline, we can account for (prelesion) tissuedifferences from spot to spot and thereby only consider ping reflectionchanges relative to that specific baseline.

Those familiar with pulse-echo work know that deeper features are harderto see because nearer field features can obstruct (mask) the deeperones. The inventors have found that excessive nearfield microbubbling ofthe extent indicative of an impending pop masks deeper lesioning makingprogress-monitoring of deeper lesions more difficult. There are a fewsolutions to this as follows. First, one can always operate the tip suchthat nearfield reflections stay under a maximum value which is below theexcessive masking level and the level known to lead to pops. This can bedone by one or both of irrigant flow adjustments (higher flows) and RFpower adjustments (lower average power and/or on/off ramp rates).Second, one can use longer delays between RF ablative power pulses andconstant cooling thereby allowing more nearfield cooling. Third, one canselectively precool the nearfield as with cooled water irrigant (lowerthan 37 Deg C. body temp) using pulsed or continuous RF ablation,preferably pulsed. In this case, the irrigant pump may become a combinedpump and water-cooler.

Of course, the system configuration illustrated in FIG. 5 is purelyexemplary of systems in which the present invention may be implemented,and the invention is not limited to a particular hardware or softwareconfiguration. The computers and storage systems implementing theinvention can also have known I/O devices (e.g., CD and DVD drives,floppy disk drives, hard drives, etc.) which can store and read themodules, programs and data structures used to implement theabove-described invention. These modules, programs and data structurescan be encoded on such computer-readable media. For example, the datastructures of the invention can be stored on computer-readable mediaindependently of one or more computer-readable media on which reside theprograms used in the invention. The components of the system can beinterconnected by any form or medium of digital data communication,e.g., a communication network. Examples of communication networksinclude local area networks, wide area networks, e.g., the Internet,wireless networks, storage area networks, and the like.

The inventive system's ability to detect lesion progress may be employedto simply inform the user to manually adjust parameters and/or may beused in a closed loop configuration wherein the system itself adjustsits own parameters as the lesioning progresses. The inventors anticipatethat at least the prepop feedback will preferably utilize a systemfeedback loop since a human user cannot react as fast as a computer toan unsafe condition.

FIG. 7 is a partial sectional view of an RF ablation tip wherein thetransducer itself is forward pointing but its beam is redirectedsideways by an acoustic mirror before exiting the ablation tip. Theacoustic mirror is employed to redirect the beam out of the tip. FIG. 7shows a catheter 61 with a mirror-based tip electrode 61 a and a polymercatheter body 61 b. The catheter 61 is immersed within a blood pool 63for forming a lesion 64 d in endocardial tissue 62 a. The catheter tipas shown has two metallic or electrically conducting parts: a rigid part61 a and a flexing part 61 a′ having flexure slots 61 a″. The rigid tipportion 61 a contains a transducer again comprised of a matching layer65 b, a piezocrystal 65 a, and an acoustic backer 65 d. Note that in thetip electrode 61 a of FIG. 7, the transducer is forward facing and emitsits beam in the distal −X direction. Note further that the tip electrode61 a contains an acoustic mirror 84 which redirects the outgoing andincoming beam 90 degrees to the longitudinal tip axis. The acoustic pathbetween the mirror 84 and transducer 65 b,a,d is filled with saline 65c′. The saline 65 c′ serves as an acoustic standoff from the tissuesurface 62 c such that the first couple of millimeters of tissue depthcan be seen without interfering transducer or cable ringdown artifacts.The mirror 84 would likely be of stainless steel or tungsten but couldalternatively be of an air-like material such as a glass microballoonfilled epoxy. A tip aperture or orifice 85 is provided at the beampath66/66 a such that the acoustic beam does not collide with the tiphousing. Presuming the tip electrode 61 a is an RF ablation electrode,then the tip container or shell would likely be formed of metal such asplatinum-iridium in the known manner. The aperture or beam-orifice 85 isdepicted as an open hole. In this manner, saline pumped into the tipcavity 65 c′ exits the orifice 85. Some smaller amount of saline mayexit small laser-drilled holes (not shown) separate from the orifice 85.Note that by having the majority of the saline exiting the tip orifice85, the tip electrode around the orifice is well-cooled despite itshaving a high RF-current density around its orifice perimeter. Further,the emanating saline serves to acoustically couple the transducer to thetissue and prevents bubbles from becoming trapped in or near chamber 65c′ or aperture 85.

The inventors specifically note that if one monitors the water pressurebeing applied to the tip from outside the patient, one can easily tellwhen the aperture 85 (and therefore the acoustic beam) is facing thetissue squarely because the back-pressure increases when the aperture issealed against the tissue. This pressure monitoring technique can beemployed manually or automatically to achieve tip-aiming and can be doneso independently or in combination with observing the actual acousticpinging feedback.

The acoustic mirror 84 may, for example, have an angle of 45 degreesresulting in a 90 degree beam exit (shown) or a different angle such as22.5 degrees resulting in a 45 degree beam exit (not shown). The mirrorthickness need only be thick enough to provide adequate reflection(e.g., 95% or better) and for metals this is actually quite thin (on theorder of microns thick). For manufacturing convenience, the mirror 84can be thicker and all metal as shown in FIG. 7 or alternatively couldcomprise micromolded polymer having a thin-film metallic coating.

D. Arrangement and Interfaces for Ablation System with Acoustic Feedback

FIG. 8 is a schematic diagram showing an ablation system with acousticfeedback as a self-contained system product. The integrated systemproduct 101 includes an RF ablation power subsystem 105, an ultrasonictransmit and receive subsystem 106, a control subsystem 104, and adisplay 107 in a self-contained package or unit. There is preferablyelectromagnetic shielding 113 employed surrounding at least one andpreferably both of the RF ablation power subsystem 105 and theultrasonic transmit and receive subsystem 106 to shield the ultrasonicreceiver from the RF energy and to shield both from the externalenvironment. The shields 113 may be provided in the form of known metalhousings, metalized plastic housings, metallic or conductive foammeshes, or the like. The fully integrated system product 101 isconnected via an operational link 103 such as a cable to a catheter 102.The catheter 102 has a catheter handle 109, a catheter body 110, and anultrasonic transducer 111 in or near the ablation electrode tip.

The RF ablation power subsystem 105 provides RF ablation power to atleast one ablation element on the catheter 102 and typically includes anRF generator. In alternative embodiments, other types of ablation powermay be employed. The ultrasonic transmit and receive subsystem 106includes circuitry or the like to operate the pulse-echo ultrasonictransducer 111 to transmit and receive acoustic pulses. The controlsubsystem 104 includes a processor and one or more modules executable bythe processor to control operation of the RF ablation power subsystem105 and the ultrasonic transmit and receive subsystem 106. The system101 preferably pulses the RF ablation power and performs ultrasonicpinging during very short ablation power pauses (e.g.,milliseconds-range pauses utilizing less than 10% and more preferablyless than 5% of the total time, the 90-95% rest of which is forablation). The control subsystem 104 provides input to the display 107to display information including the lesion depth and prepop/popinformation and other results from the ultrasonic transducer 111 andprocessed by the control subsystem, as well as operating parameters andsettings. Examples of information to be displayed include RF ablationinformation (e.g., power, temperature, time, peak temperature,integrated power, power plots, temperature plots, and the like), patientvitals, spatial navigation and mapping, images of imaging device (e.g.,ultrasound, OCT, IR, and the like), and electrode tip force feedback.The control subsystem 104 is connected with the RF ablation powersubsystem 105, the ultrasonic transmit and receive subsystem 106, andthe display 107 via internal operational links 108. The controlsubsystem 104 may include the ablation logic unit 8A, the control andinterface system 10 including the lesion depth correction module 10 abut excluding the display, and the optional 3D navigation/modelingsystem unit 12 of FIG. 5. The ultrasonic transmit and receive subsystem106 may include the pinger send/receive power/logic unit 9 of FIG. 5.

FIG. 9 shows an example of a block diagram of the control subsystem 104of FIG. 8. The control subsystem 104 includes a CPU 120, an ablationpower control module 124 to control the RF ablation power subsystem 105to provide RF ablation power, an ultrasonic control module 126 tocontrol the ultrasonic transmit and receive subsystem 106 to transmitand receive acoustic pulses, and a transducer detection informationprocessing module 128 to process transducer detected information fromthe pulse-echo ultrasonic transducer 111 and to provide feedback, basedon the processed transducer detected information, to be used to controlablation by the at least one ablation element. In addition, if amanipulation mechanism (see, e.g., robot 13B in FIG. 5) is provided tomanipulate the distal portion of the catheter body in movement includingrotation of at least the distal portion of the catheter around thelongitudinal axis, a manipulation mechanism control module 130 may beprovided to control the manipulation mechanism to rotate at least thedistal portion of the catheter body. The tip rotation may be responsiveto the transducer feedback. The modules may be implemented in software,firmware, or other forms. If implemented in software, for instance, themodules can be stored in a memory 122. Alternatively, the modules can beimplemented in hardware on circuitry 122. Of course, different modulesor additional modules are possible in other embodiments.

In preferred embodiments the transducer detection information processingmodule 128 would run the at least one algorithm on the receivedultrasound reflection signals arranged to perform one or both ofdeducing a lesion depth or detecting prepop or pop activity. In someembodiments, the transducer detected information includes a detectedlesion depth along a beam emanation direction. The transducer detectioninformation processing module 128 includes a lesion depth correctionmodule (see, e.g., module 10A in FIG. 5) which converts the detectedlesion depth along the beam direction to a corrected lesion depth in anormal direction which is perpendicular to the tissue surface in contactwith the at least one ablation element. Processing the transducerdetection information by the transducer detection information processingmodule comprises at least one of: determining a lesion depth along thebeam line, determining a corrected lesion depth not along the beam line,determining lesion-making progress, determining a tissue thickness,determining lesion transmurality, identifying activity indicative ofprepopping or popping, providing an audible and/or visual feedbackwarning of prepopping, determining a rotation state of the distalportion, and determining a distance from the distal portion to thetissue surface from within a blood pool. Some of these features aredescribed above. In addition, the ablation power control module 124 maybe configured, in response to the identified activity indicative ofprepopping, to adjust the ablation power duty cycle or ramp-rate orchange the irrigant flow rate to reduce a chance for popping.

The self-contained system product 101 of FIG. 8 may include othercomponents or features. For example, a user interface (e.g., GUI of thecontrol and interface system 10 in FIG. 5) may be provided to receiveinput from a user to be displayed or to be used for executing themodules of the control subsystem 104.

FIG. 10 is a schematic diagram showing an ablation system with acousticfeedback in the form of a tablet-like system control and acousticfeedback processing product coupled with an ablation power subsystemproduct. The ablation power subsystem product 201 a includes an RFablation power subsystem 205 and is connected via a first operationallink 203 a such as a cable to a catheter 102 which has the catheterhandle 109, catheter body 110, and ultrasonic transducer 111. Thetablet-like system control and acoustic feedback processing product 201b includes an ultrasonic transmit and receive subsystem 206, a controlsubsystem 204, a display 207, and internal operational links 208, andthe product 201 b is connected via a second operational link 203 b suchas a cable to the catheter 102. The system control and acoustic feedbackprocessing product 201 b may be packaged as a tablet, a handheld device,a flat screen device, or the like. The system control and acousticfeedback processing product 201 b may be configured to be plugged into aPC or a network to upload a study (powers, times, lesion depths, vitals,etc.) or other information. It may have wireless capability to form anoperational link with other devices. While FIG. 10 shows a display 207in the system control and acoustic feedback processing product 201 b, inother embodiments, the display may be provided in the ablation powersubsystem product 201 a instead of or in addition to the display in thesystem control and acoustic feedback processing product 201 b. The twooperational links 203 a, 203 b may include two separate cables or asingle cable which runs through both packages 201 a, 201 b forconnection to the catheter 102. The display 207 is preferably a colortouch screen display also employed to input data and commands.

There are a number of differences between the two package configurationof FIG. 10 and the single package configuration of FIG. 8. As a separatepackage, the ablation power subsystem product 201 a containing the RFablation power subsystem 205 may essentially be an existing RF ablationgenerator without much modification. Some minor upgrade in software andthe addition of a BNC (Bayonet Neill-Concelman) power-triggeringconnector may be sufficient to enable its operability with the separatesystem control and acoustic feedback processing product 201 b. Incontrast, the RF ablation power subsystem 105 of FIG. 8 may requiresignificant modifications to be integrated into the self-containedsystem 101. The shielding 113 in the self-contained system product 101of FIG. 8 may also be used in the system of FIG. 10 (not shown);however, the electromagnetic noise potential in the system of FIG. 8 ismuch more severe. There may also be more design latitude and choices forusing existing processors, ultrasound boards, and the like to assemblethe system control and acoustic feedback processing product 201 b asopposed to the self-contained system product 101. The system control andacoustic feedback processing product 201 b may be designed to work withany triggerable RF ablation generator of the ablation power subsystemproduct 201 a, making it more versatile and adaptable.

It is possible to place the system control and acoustic feedbackprocessing product 201 b in the sterile field apart from the ablationpower subsystem product 201 a. The product 201 b can be configured to besuitable for operation in a sterile field such as by putting it into adisposable clear enwrapping bag or by designing it to be sterilantwipable.

In the description, numerous details are set forth for purposes ofexplanation in order to provide a thorough understanding of the presentinvention. However, it will be apparent to one skilled in the art thatnot all of these specific details are required in order to practice thepresent invention. Additionally, while specific embodiments have beenillustrated and described in this specification, those of ordinary skillin the art appreciate that any arrangement that is calculated to achievethe same purpose may be substituted for the specific embodimentsdisclosed. For example, the tip electrode may also serve as a sensing,pacing, or navigation electrode, or may be situated nearby suchadditional unshared electrodes. This disclosure is intended to cover anyand all adaptations or variations of the present invention, and it is tobe understood that the terms used in the following claims should not beconstrued to limit the invention to the specific embodiments disclosedin the specification. Rather, the scope of the invention is to bedetermined entirely by the following claims, which are to be construedin accordance with the established doctrines of claim interpretation,along with the full range of equivalents to which such claims areentitled.

What is claimed is:
 1. A system for ablation with acoustic feedback, thesystem comprising: a catheter which includes an elongated catheter bodyextending longitudinally between a proximal end and a distal end along alongitudinal axis; at least one ablation element disposed in a distalportion which is adjacent the distal end of the catheter body to ablatea targeted tissue region outside the catheter body; and a pulse-echoultrasonic transducer disposed in the distal portion and arranged toemit and receive an acoustic beam along a centroid in a beam direction,at a transducer beam angle of between about 30 degrees and about 60degrees relative to a distal direction of the longitudinal axis at alocation of intersection between the longitudinal axis and the beamdirection of the centroid of the acoustic beam of the ultrasonictransducer, wherein the pulse-echo ultrasonic transducer transmits andreceives acoustic pulses to provide lesion information in the targetedtissue region being ablated; an ablation power subsystem to provideablation power to the at least one ablation element; an ultrasonictransmit and receive subsystem to operate the pulse-echo ultrasonictransducer to transmit and receive acoustic pulses; a control subsystemwhich includes a processor and one or more modules executable by theprocessor to control operation of the ablation power subsystem and theultrasonic transmit and receive subsystem; and a display to displayinformation including the lesion information; wherein the one or moremodules include a transducer detection information processing module toprocess transducer detected information from the pulse-echo ultrasonictransducer and to provide feedback, based on the processed transducerdetected information, to be used to monitor or control ablation by theat least one ablation element; wherein the transducer detectedinformation includes a detected lesion depth along a beam emanationdirection; and wherein the transducer detection information processingmodule includes a lesion depth correction module which converts thedetected lesion depth along the beam direction to a corrected lesiondepth in a normal direction which is perpendicular to the tissue surfacein contact with the at least one ablation element.
 2. The system ofclaim 1, further comprising: a single package containing the ablationpower subsystem, the ultrasonic transmit and receive subsystem, thecontrol subsystem, and the display; and an operational link coupledbetween the single package and the catheter.
 3. The system of claim 1,further comprising: a first package containing the ablation powersubsystem and none of the ultrasonic transmit and receive subsystem andthe control subsystem; a second package separate from the first packageand containing one or more of the ultrasonic transmit and receivesubsystem, the control subsystem, or the display; a first operationallink coupled between the first package and the catheter; and a secondoperational link coupled between the second package and the catheter. 4.The system of claim 3, wherein the second package is selected from thegroup consisting of a handheld device, a tablet, a flat screen, and atouch-screen device.
 5. The system of claim 3, wherein only one of thefirst package and the second package contains the display.
 6. The systemof claim 3, wherein the first package has a first display and the secondpackage has a second display.
 7. The system of claim 1, wherein the oneor more modules include at least one of: an ablation power controlmodule to control the ablation power subsystem to provide ablationpower; and an ultrasonic control module to control the ultrasonictransmit and receive subsystem to transmit and receive acoustic pulses.8. The system of claim 1, wherein processing the transducer detectioninformation by the transducer detection information processing modulecomprises at least one of: determining an uncorrected or correctedlesion depth; determining lesion-making progress; determining a tissuethickness; determining lesion transmurality; identifying activityindicative of prepopping or popping; providing an audible feedbackwarning of prepopping; determining a rotation state of the distalportion; and determining a distance from the distal portion to thetissue surface from within a blood pool.
 9. The system of claim 1,wherein processing the transducer detection information by thetransducer detection information processing module comprises identifyingactivity indicative of prepopping; wherein the one or more modulescomprise an ablation power control module to control the ablation powersubsystem to provide ablation power; and wherein the ablation powercontrol module is configured, in response to the identified activityindicative of prepopping, to adjust at least one of an ablation power, aduty-cycle or ramp-rate, and an ablation irrigant flow rate to reduce achance for popping.
 10. The system of claim 1, further comprising: auser interface to receive input from a user to be displayed or to beused for executing the one or more modules by the processor.
 11. Thesystem of claim 1, wherein only one pulse-echo ultrasonic transducer isprovided in the catheter.
 12. The system of claim 1, further comprising:a manipulation mechanism to manipulate the distal portion of thecatheter body in movement including rotation of at least the distalportion of the catheter around the longitudinal axis; wherein the one ormore modules include a manipulation mechanism control module to controlthe manipulation mechanism to rotate at least the distal portion of thecatheter body.
 13. A system for ablation with acoustic feedback, thesystem comprising: a catheter which includes an elongated catheter bodyextending longitudinally between a proximal end and a distal end along alongitudinal axis; at least one ablation element disposed in a distalportion which is adjacent the distal end of the catheter body to ablatea targeted tissue region outside the catheter body; and a pulse-echoultrasonic transducer disposed in the distal portion and arranged toemit and receive an acoustic beam along a centroid in a beam direction,at a transducer beam angle of between about 30 degrees and about 60degrees relative to a distal direction of the longitudinal axis at alocation of intersection between the longitudinal axis and the beamdirection of the centroid of the acoustic beam of the ultrasonictransducer, wherein the pulse-echo ultrasonic transducer transmits andreceives acoustic pulses to provide lesion information in the targetedtissue region being ablated; an ablation power subsystem to provideablation power to the at least one ablation element; an ultrasonictransmit and receive subsystem to operate the pulse-echo ultrasonictransducer to transmit and receive acoustic pulses; a control subsystemwhich includes a processor and one or more modules executable by theprocessor to control operation of the ablation power subsystem and theultrasonic transmit and receive subsystem; a display to displayinformation including the lesion information; and a single packagecontaining the ablation power subsystem, the ultrasonic transmit andreceive subsystem, the control subsystem, and the display; wherein theone or more modules include a transducer detection informationprocessing module to process transducer detected information from thepulse-echo ultrasonic transducer and to provide feedback, based on theprocessed transducer detected information, to be used to monitor orcontrol ablation by the at least one ablation element; wherein thetransducer detected information includes a detected lesion depth along abeam emanation direction; and wherein the transducer detectioninformation processing module includes a lesion depth correction modulewhich converts the detected lesion depth along the beam direction to acorrected lesion depth in a normal direction which is perpendicular tothe tissue surface in contact with the at least one ablation element.14. The system of claim 13, wherein the ablation power subsystemcomprises an RF generator to provide RF ablation power to the at leastone ablation element; the system further comprising: one or moreelectromagnetic shields to prevent at least one of electromagneticinterference between the subsystems within the system or electromagneticinterference between the subsystems and external equipment outside thesystem.
 15. A system for ablation with acoustic feedback, the systemcomprising: a catheter which includes an elongated catheter bodyextending longitudinally between a proximal end and a distal end along alongitudinal axis; at least one ablation element disposed in a distalportion which is adjacent the distal end of the catheter body to ablatea targeted tissue region outside the catheter body; and a pulse-echoultrasonic transducer disposed in the distal portion and arranged toemit and receive an acoustic beam along a centroid in a beam direction,at a transducer beam angle of between about 30 degrees and about 60degrees relative to a distal direction of the longitudinal axis at alocation of intersection between the longitudinal axis and the beamdirection of the centroid of the acoustic beam of the ultrasonictransducer, wherein the pulse-echo ultrasonic transducer transmits andreceives acoustic pulses to provide lesion information in the targetedtissue region being ablated; an ablation power subsystem to provideablation power to the at least one ablation element; an ultrasonictransmit and receive subsystem to operate the pulse-echo ultrasonictransducer to transmit and receive acoustic pulses; a control subsystemwhich includes a processor and one or more modules executable by theprocessor to control operation of the ablation power subsystem and theultrasonic transmit and receive subsystem; a display to displayinformation including the lesion information; a first package containingthe ablation power subsystem and none of the ultrasonic transmit andreceive subsystem and the control subsystem; and a second packageseparate from the first package and containing one or more of theultrasonic transmit and receive subsystem, the control subsystem, or thedisplay; wherein the one or more modules include a transducer detectioninformation processing module to process transducer detected informationfrom the pulse-echo ultrasonic transducer and to provide feedback, basedon the processed transducer detected information, to be used to monitoror control ablation by the at least one ablation element; wherein thetransducer detected information includes a detected lesion depth along abeam emanation direction; and wherein the transducer detectioninformation processing module includes a lesion depth correction modulewhich converts the detected lesion depth along the beam direction to acorrected lesion depth in a normal direction which is perpendicular tothe tissue surface in contact with the at least one ablation element.16. The system of claim 15, wherein the second package is selected fromthe group consisting of a handheld device, a tablet, a flat screendevice, and a touch-screen device.
 17. The system of claim 15, whereinthe second package is configured to be suitable for operation in asterile field.
 18. The system of claim 15, wherein the second packagecontains the display.
 19. The system of claim 15, further comprising: afirst operational link coupled between the first package and thecatheter; and a second operational link coupled between the secondpackage and the catheter.
 20. The system of claim 15, wherein the one ormore modules include at least one of: an ablation power control moduleto control the ablation power subsystem to provide ablation power; andan ultrasonic control module to control the ultrasonic transmit andreceive subsystem to transmit and receive acoustic pulses.